We have demonstrated insulin, lactogen, and other polypeptide hormone receptors in Golgi elements of rat liver and have shown that both insulin and prolactin are internalized and concentrated at these intracellular sites. We wish to extend these studies to glucagon, an adenyl cyclase stimulator, and to confirm our preliminary observations of a second intracellular receptor pool in lysosomes, prepared both as tritosomes and in a more "natural" form using metrizamide gradient centrifugation. A biogenetic role for the Golgi receptors will be examined by following the time course of change of lactogen receptor in Golgi and plasmalemma (PM) during rapid disappearance of the receptor with and without the blockade of exocytosis by colchicine. The possibility that Golgi and PM receptors are regulated in a reciprocal manner will be evaluated by studying states of hormone excess and deficiency. The internalization of polypeptide hormones will be further studied by evaluating 125I-glucagon uptake, attempting to isolate endocytotic vesicles, and trying to extract native peptide hormones from subcellular fractions. To evaluate more fully the mechanism of internalization we shall study both in vivo and in liver perfusion the effects of agents which influence energy metabolism, microfilament function, and receptor diffusion, as well as agents which alter hepatic proteolytic activity, especially chloroquine. The uptake of insulin into lysosomes and Golgi will be studied to seek a correlation of the state of insulin sensitivity and the intracellular distribution of internalized hormone. In vivo radioautography will continue to be used as a vital complement to the cell fractionation studies, a uniquely effective method of identifying hormone-sensitive target cells in multi-cellular organs, and a way of examining the internalization process in many tissues for which subcellular fractionation has not been refined.